Low cost 3D bio-carbon foams obtained from wheat straw with broadened bandwidth electromagnetic wave absorption performance

Bio-derived dielectrics have drawn extensive attention for microwave absorption and shielding because of renewability and environmental friendliness. In this work, foam-like bio-carbon has been obtained from wheat straw waste and its microwave absorption performance has been studied. By controlling the precursor ratio of KOH, the optimized morphology of bio-carbon has been realized. The 3D carbon foam obtained at 600 degrees C with KOH and biomass ratio 1:1 (AC-600 (1:1), presents decent microwave reflection loss. Especially, with a low absorber ratio (10 wt%), the effective absorption bandwidth (RL <-10 dB) can reach 8.8 GHz (7.2-16 GHz) at a matching thickness of 2.5 mm. 3D porous network, interface effect, defects in carbon network, and dipolar relaxation make a good contribution towards broadband and excellent reflection loss. The eco-friendly, lightweight, and low-cost bio-carbon foam has great application prospects of microwave absorption.